Tour giant's causeway from Belfast

This past summer we took one with PaddyWagon tours. It also included a stop at Dunluce Castle and the Dark Hedges. We felt it was adequate, had no complaints but nothing special. There wasn’t a ton of time at Giants Causeway but we were able to walk down to the stones, explore a little/take photos and walk back with time to spare, so it was adequate for us. It wasn’t a terribly long day and we were back in Belfast before 6:00pm, I think. Everything went off as advertised. The guide was also the bus driver. He provided commentary along the way, but didn’t guide us at any of the stops-those were independent.

We chose a tour since we didn’t rent a car while in Belfast. And also because we had some PaddyWagon credit from a 2020 itinerary to Ireland that didn’t happen due to Covid. They honored our credit 4 years later which I thought was a plus.

The Things to Do menu on Trip Advisor has a number of day tours from Belfast up to the causeway.
We've always found reviews of the various companies on their website to be pretty reliable.

I also took the Paddywagon tour this summer. The guide offered to arrange a Black Cab tour at the end if anyone wanted. I wouldn't recommend doing the Black Cab tour at the end of a long day, but if you're strapped for time, it's an option. I think we were back in Belfast by 4:30.
If you search the forum, you should find the public transit options for getting out there, as well.